In recent years, soft silicone hydrogel contact lenses, for example, Focus NIGHT & DAY™ and AIROPTIX™ (CIBA VISION), and PureVision™ (Bausch & Lomb) become more and more popular because of their high oxygen permeability and comfort. “Soft” contact lenses conform closely to the shape of the eye, so oxygen cannot easily circumvent the lens. Soft contact lenses must allow oxygen from the surrounding air (i.e., oxygen) to reach the cornea because the cornea does not receive oxygen from the blood supply like other tissue. If sufficient oxygen does not reach the cornea, corneal swelling occurs. Extended periods of oxygen deprivation cause the undesirable growth of blood vessels in the cornea. By having high oxygen permeability, a silicone hydrogel contact lens allows sufficient oxygen permeate through the lens to the cornea and to have minimal adverse effects on corneal health.
However, a silicone hydrogel material typically has a surface or at least some areas of its surface which is hydrophobic (non-wettable). Lipids or proteins from the ocular environment can be adsorbed onto hydrophobic surface or surface areas of a silicone hydrogel contact lens. The hydrophobic surface or surface areas of a silicone hydrogel contact lens may cause it be adhered to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification to increase surface hydrophilicity.
A known method for modifying the hydrophilicity of a relatively hydrophobic contact lens material is to attach hydrophilic polymers onto contact lenses according to various mechanisms (see for example, U.S. Pat. Nos. 6,099,122, 6,436,481, 6,440,571, 6,447,920, 6,465,056, 6,521,352, 6,586,038, 6,623,747, 6,730,366, 6,734,321, 6,835,410, 6,878,399, 6,923,978, 6,440,571, and 6,500,481, US Patent Application Publication Nos. 2009/0145086 A1, 2009/0145091A1, 2008/0142038A1, and 2007/0122540A1, all of which are herein incorporated by reference in their entireties). Although those techniques can be used in rendering a silicone hydrogel material wettable, they may not be cost-effective and/or time-efficient for implementation in a mass production environment, because they typically require relatively long time and/or involve laborious, multiple steps to obtain a hydrophilic coating.
The amino groups and or carboxyl groups introduced on and or the surface of silicone hydrogel contact lens render the lenses hydrophilic, i.e. they wet easily and absorb water and also contribute to lens hydrophilic character. With water absorption, the lenses also may take up chemicals dissolved in the water. When contact lens care products containing compounds bearing positive charges are used with the contact lenses, an ionic interaction can take place between the contact lenses and those components. Use of products containing such components can produce undesirable clinical symptoms in some persons, such as diffuse corneal staining and product intolerance.
The most common preservatives and disinfecting agents known are Polyhexamethylenebiguanide (PHMB), polymeric quaternary ammonium compound such as Polyquaternium-1® and other positively charged preservatives. It was found that many of these preservatives and disinfecting agents become concentrated in the lenses to a sufficient degree that when the lens is placed in the aqueous environment of the eye, the preservatives or disinfectants are released from the lens and cause eye irritation. This problem was found to be particularly severe with positively charged preservatives or disinfecting components.
Therefore, there is a need for a cost-effective and time-efficient method for reducing hydrophilic silicone hydrogel contact lens' positively charged preservatives such as PHMB uptake. There is still a need for a cost-effective and time-efficient method of applying a crosslinked hydrophilic coating onto a silicone hydrogel contact lens to reduce its positively charged preservatives such as PHMB uptake and to improve its hydrophilicity and lubricity. In addition, the present invention provides an ophthalmic lens product